“You can’t run government without being able to have confidential discussions with people on issues that are of profound importance... you make politicians very nervous of actually debating things honestly, because they’re worried about what’s going to happen when there’s a FoI request”.

Maurice Frankel, director of the Campaign for Freedom of Information, responded: “The problem isn’t that these disclosures make frank discussions inside government harder, as Blair claims. It’s that the disclosures make not telling the truth harder”.

Frankel argues that FoI “has strengthened the rights of the citizen to know what public authorities are really doing”.

In his view he “has become a potent tool to help people understand where public services are falling short” to “discover whether government is fulfilling its promises “ and to “hold those in power to account”.

That certainly vindicates those political leaders who supported the campaign when it was launched in 1984. They included the three main opposition party leaders: Neil Kinnock, David Steel and David Owen.

But it was opposed by the then prime minister, Margaret Thatcher. She argued, as Blair did later, that a legal power to force ministers to disclose information would weaken ministers’ accountability to parliament.

By the time Labour came to power in 1997 it had promised FoI in six successive election manifestos. Blair said then that FoI would “signal a new relationship between government and people”.

In his autobiography, however, he described FoI as his biggest mistake and reproached himself as a “nincompoop” for introducing it.

Fortunately, it remains on the statute book despite its unpopularity with government, and a series of attempts to restrict it are likely to continue.

These have included (so far unsuccessful) proposals to allow authorities to refuse thousands of additional requests on cost grounds, to remove parliament from the act and to block access to papers circulated to cabinet or cabinet committees.

There has also been pressure to exempt all government policy discussions regardless of the public interest and to introduce charges for requests.